The subject invention concerns improvements to a drinking cup of a kind which is manufactured from a resilient, flexible synthetic resin material and which is intended for repeated use.
On various occasions, expandable cups are used for coffee and other beverages, either for convenience or because no service personnel is available for washing up. The extensive use of expendable articles of this kind has been widely discussed lately. The critics claim that the use of expendable articles is a considerable waste of natural resources and energy and often leads to environmental pollution.
In Swedish Pat. 409 645 granted Dec. 20, 1979 is disclosed a cup intended for use on the occasions outlined above. This cup, which is manufactured from a resilient and flexible synthetic resin material and which is intended for repeated use, has a lower, preferably cylindrical section, and an upper section essentially in the shape of a truncated cone, which cone-shaped section may be turned downwards and folded upon the lower section to reduce the volume of the cup.
Cups of this kind suffer from certain drawbacks. The round shape make them difficult to drink from. On account of the comparatively weak structure of such cups in the area of the handle, folding of the upper section downwards as well as raising the section involves certain difficulties.
Another known constructions for similar purposes is the collapsible tumbler. The tumbler consists of several parts which are slidable into each other. These parts can be locked relative to one other in a position in which the tumbler serves as a drinking cup and be folded together to a compact position. The main disadvantage inherent in this construction is leakage of the cup due to the wear between the parts.